Reproducibility and Clinical Implications of Masked Hypertension Hypertension-the most important cardiovascular disease (CVD) risk factor-can go undetected for one of two main reasons: either a person's blood pressure (BP) is simply not checked (i.e., the person is not screened), or the screening measurement itself does not detect it. Over the past four decades, much effort has been devoted to improving screening rates for detection of high BP. Only recently, however, through the use of 24-hour ambulatory BP monitoring (ABPM), has attention been given to the possibility that "false negative" office BP measurements may be substantial in number and clinically important. Masked hypertension (MH) denotes BP that is not elevated (<140/90 mm Hg) when measured in the office, but elevated when repeated measurements are averaged over the course of a day. The prevalence of MH in the general adult population is estimated to be 10%. Recent data suggest that people with MH have cardiovascular target organ damage and an increase in CVD events of an order of magnitude approaching that seen in people with sustained hypertension (elevated office BP levels with elevated out-of-office BP levels). Many important unresolved questions need to be answered, however, before clinical recommendations can be made. Chief among these is whether MH represents a reproducible phenomenon. Another important consideration is clarifying whether home BP monitoring (HBPM) can be used in place of ABPM to identify MH, and if so, whether it serves to identify the same at-risk population. We aim to (1) assess the reproducibility of MH and evaluate the agreement between HBPM and ABPM in identifying MH, (2) identify demographic, psychosocial, and clinical factors associated with MH, and (3) explore the degree of target organ damage and subclinical atherosclerosis associated with MH. To accomplish these aims, we will perform two sets of office, ABPM, and HBPM BP measurements one week apart on 420 adults not under treatment for hypertension recruited from twelve primary care practices. Other measures will include serum glucose, lipids, and C-reactive protein;urine albumin;left ventricular mass index;coronary artery calcium;perceived stress;job and home strain;and trait-anger. The research team has extensive experience with BP measurement research, psychosocial effects on BP, cardiac imaging methods, coronary heart disease risk assessment, and conducting research in networks of primary care practices. Our study is expected to improve our understanding of the epidemiology and implications of MH and ultimately lead to strategies that will improve detection of high BP in the population. PUBLIC HEALTH RELEVANCE: The possibility that office blood pressure measurements fail to detect hypertension for millions of people demands the kind of rigorous investigations described in the proposed study. The findings are expected to lead to clinical strategies enabling greater recognition of hypertension, and therefore, ultimately to a reduction in cardiovascular morbidity and mortality in the population.